So I pulled the code on my 328i and this is what I got

"E90M3" (e90m3)
03/25/2019 at 14:32 • Filed to: None

P0050 and P0155, seems to be an O2 sensor this time. Just need to figure out which O2 sensor it is, since there are 4 and replace it.

DISCUSSION (29)

random001 > E90M3
03/25/2019 at 14:35

It’s bank 2, sensor 1, obviously....

E90M3 > random001
03/25/2019 at 14:36

Ah yes, bank 2 on my inline 6.

I know you had an overtone of sarcasm on that comment.

Nibby > E90M3
03/25/2019 at 14:38

time for a new E90

random001 > E90M3
03/25/2019 at 14:39

Heh! Well, you should have two sets of three cylinders feeding a cat each, so that bad sensor should be the rear set, pre-cat sensor.

I don’t remember if these are spit 1/2 or 1/2/1/2/1/2 into the 3-2-1 manifold. Should not be a 6-1 manifold, because that’s ridiculous.

Arch Duke Maxyenko, Shit Talk Extraordinaire > E90M3
03/25/2019 at 14:39

I6-Bank 1 = 1,2,3

Bank 2= 4,5,6

Urambo Tauro > E90M3
03/25/2019 at 14:41

Like this?

Kinja'd!!!

E90M3 > Arch Duke Maxyenko, Shit Talk Extraordinaire
03/25/2019 at 14:44

I hadn’t seen anything in my quick google search and I was really hoping that wasn’t the case, because is harder to get to. I’m going to change this one myself.

E90M3 > Nibby
03/25/2019 at 14:44

More like a Benz.

For Sweden > E90M3
03/25/2019 at 14:45

My S80 has a straight six and two banks.

RallyWrench > E90M3
03/25/2019 at 14:47

That’s the pre-Cat sensor for cylinder 4-6, in the manifold.

Nibby > E90M3
03/25/2019 at 14:48

which one?

Future Heap Owner > E90M3
03/25/2019 at 14:52

What’s the procedure to pinpoint the bad sensor? Is testing voltage/resistance a reliable way to find a bad one? Or do you have to start removing or replacing them and see how the codes change?

diplodicus forgot his password > E90M3
03/25/2019 at 14:53

cylinders 4-6, sensor upstream of cat.

E90M3 > Future Heap Owner
03/25/2019 at 14:53

Going to assume the sensor is bad and replace it. If that doesn’t work, then I’ll probably approach it differently.

E90M3 > Nibby
03/25/2019 at 14:54

Facelifted W204 C300.

dogisbadob > E90M3
03/25/2019 at 14:55

You might as well replace both upstream sensors anyway since the other one is on its way out

Future Heap Owner > E90M3
03/25/2019 at 15:02

Oh, I thought you didn’t know which sensor was the bad one.

Nibby > E90M3
03/25/2019 at 15:12

meh get the current gen instead much nicer car

RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars > E90M3
03/25/2019 at 15:26

I have the same tester! :D

E90M3 > RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars
03/25/2019 at 15:30

It’s actually a coworkers, I do need to get one though.

E90M3 > Nibby
03/25/2019 at 15:30

I don’t like the way they look and they’re more money , they do drive really nice thought. I didn’t think the W204 is a bad car.

RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars > E90M3
03/25/2019 at 15:31

They are pretty handy!

E90M3 > Future Heap Owner
03/25/2019 at 15:31

I wasn’t too sure, because I didn’t know what bank 2 meant. I assumed it was the back cylinders, but then you never know, seems this post cleared it up.

E90M3 > dogisbadob
03/25/2019 at 15:32

Maybe, this one is going to be a pain to get to, the other is right there. I think I’m going to replace just one and see if that fixes it. If that does, might change the other one as well.

KingT- 60% of the time, it works every time > E90M3
03/25/2019 at 15:36

2013 and on C300 has the detuned 3.5, it’s faster.

https://www.caranddriver.com/reviews/a15111815/2013-mercedes-benz-c300-4matic-sedan-test-review/

E90M3 > KingT- 60% of the time, it works every time
03/25/2019 at 15:45

Are they only 4matic? I feel like I’ve only seen 4matics.

In all seriousness, I’m changing the O2 sensor and hoping that makes my CEL disappear.

KingT- 60% of the time, it works every time > E90M3
03/25/2019 at 15:45

only 4Matics on C300s in that refresh

E90M3 > KingT- 60% of the time, it works every time
03/25/2019 at 15:46

Ah, that makes sense now.

pip bip - choose Corrour > E90M3
03/26/2019 at 04:02

replace them all in one go